The invention generally relates to the fuel cells, and specifically to solid oxide regenerative fuel cells.
A solid oxide fuel cell (SOFC) is an electrochemical device that converts chemical energy directly into electrical energy. A Solid Oxide Regenerative Fuel Cell (SORFC) is an electrochemical device that converts chemical energy directly into electrical energy and subsequently reconverts electrical energy back to the original chemical energy. This device differs significantly from rechargeable batteries in that the chemicals are stored outside of the SORFC converter. The SORFC system has many building electrical energy storage applications that cannot be satisfied by batteries. For example, a SORFC system for building power generation is discussed in the Proceedings of the 2001 DOE Hydrogen Program Review NREL/CP-570-30535. The SORFC requires additional heat to vaporize stored water that will be electrolyzed during charge mode. This increases the cost and decreases the efficiency of the SORFC operation.
In one preferred aspect of the present invention, there is provided a method of operating a regenerative fuel cell system, comprising providing a fuel and oxidizer into a fuel cell during discharge mode, storing waste heat generated by the fuel cell during the discharge mode, heating water using the stored waste heat during charge mode, and electrolyzing the heated water in the fuel cell during the charge mode.
In another preferred aspect of the present invention, there is provided a fuel cell system comprising a regenerative fuel cell and a heat storage material which is adapted to store waste heat from the fuel cell during discharge mode and which is adapted to heat water provided into the fuel cell for electrolyzation during charge mode.